1. Field of the Invention
This invention relates to a z-axis interconnect and, more specifically, to an interconnect for high frequency signals between adjacent locations, such as, for example, circuit boards, semiconductor devices and the like.
2. Brief Description of the Prior Art
It is well known that the transmission of high frequency signals, such as, for example, between two components, such as, for example, between a circuit board and a pad on a semiconductor chip secured thereon, is adversely affected by misalignment of the interconnect structure between the pad and board and impedance mismatch between the pad and board. Such misalignment causes impedance mismatches leading to reflections of microwave signals at the interface and high insertion loss through the interface. Accordingly, in order to insure high quality performance of the equipment, great care must be taken to insure proper alignment of the interconnect structure with the components being interconnected. The present options are (1) to fabricate equipment, taking precautions to control misalignment on a cost/benefit basis, this approach often resulting in low yield and/or poor quality or (2) taking great care to insure proper alignment, this being a tedious and time consuming operation which greatly increases the cost of fabrication on a per unit basis. In general, prior art interconnects derive substantial inductance in vias which are not referenced to a ground plane and minimal capacitance mainly from pad structures. It is therefore difficult to alter the electrical characteristics once mismatch has occurred due to misalignment. Typical prior art systems of the type discussed above are disclosed in D. Strack et al., "Solder Free Interconnects for Mixed Signal (DC/Microwave) Systems", 1996 IEEE International Microwave Symposium, pp. 231-234, R. Sturdivant et al., "Transitions and Interconnects Using Coplanar waveguide and Other Three Conductor Transmission Lines", 1996 IEEE International Symposium, pp. 235-238 and F. Colomb et al., "Characterization of Metal on Elastomer Vertical Interconnections", 1996 IEEE International Symposium, pp. 75-77.
It is therefore apparent that a new and/or improved technique for controlling misalignment and/or the results thereof in high frequency interconnects which can provide high quality and yield and also minimize costs is highly desirable.